Catalyst and process using the catalyst

ABSTRACT

A new chromium-containing fluorination catalyst is described. The catalyst comprises an amount of zinc that promotes activity and from 0.1 to 8.0% by weight of the chromium in the catalyst based on the total weight of the chromium is present as chromium (VI). The use of the zinc-promoted, chromium-containing catalyst in a fluorination process in which a hydrocarbon or halogenated hydrocarbon is reacted with hydrogen fluoride in the vapor-phase at elevated temperatures is also described.

This invention relates to a chromium-containing fluorination catalystand to a process for the production of fluorinated hydrocarbons thatuses the catalyst. More particularly, the invention relates to a zincpromoted, chromium-containing fluorination catalyst and to a process forthe production of a fluorinated hydrocarbon in which an alkene orhalogenated hydrocarbon is reacted with hydrogen fluoride in thepresence of the catalyst.

The production of fluorinated hydrocarbons, which may also containhalogen atoms other than fluorine, by the catalysed vapour-phasefluorination of alkenes or halogenated hydrocarbons with hydrogenfluoride is well known and numerous catalysts have been proposed for usein such processes. Catalysts containing and typically based on chromium,and in particular chromia, are frequently employed in the knownprocesses. Thus, for example, chromia or a halogenated chromia may beused in the vapour-phase reaction of trichloroethylene with hydrogenfluoride to produce 1-chloro-2,2,2-trifluoroethane as described inGB-1,307,224 and in the vapour-phase reaction of1-chloro-2,2,2-trifluoroethane with hydrogen fluoride to produce1,1,1,2-tetrafluoroethane as described in GB-1,589,924. The samecatalyst may also be used for the fluorination of chlorodifluoroethyleneto 1-chloro-2,2,2-trifluoroethane, for example in a process for theremoval of chlorodifluoroethylene impurity from1,1,1,2-tetrafluoroethane as also described in GB-1,589,924.

EP-A-0502605 discloses a chromium-containing fluorination catalyst whichcomprises an activity-promoting amount of zinc or a compound of zinc.The catalyst can be used in a process for preparing1,1,1,2-tetrafluoroethane in which 1-chloro-2,2,2-trifluoroethane isreacted with hydrogen fluoride in the presence of the catalyst toproduce the 1,1,1,2-tetrafluoroethane. The1-chloro-2,2,2-trifluoroethane may be prepared by reactingtrichloroethylene with hydrogen fluoride in the presence of the samecatalyst.

Manufacturers of fluorinated hydrocarbons are always seeking improvedcatalysts for use in the manufacture of those compounds. It has now beenfound that the performance of chromium-containing catalysts containingcontrolled amounts of zinc may be augmented if some of the chromium inthe catalyst is present as chromium (VI).

SUMMARY OF THE INVENTION

According to the present invention there is provided achromium-containing fluorination catalyst which comprises an amount ofzinc and wherein from 0.1 to 8.0% by weight of the chromium in thecatalyst based on the total weight of said chromium is present aschromium (VI).

The present inventors have found that small amounts of chromium (VI) inthe catalyst can improve catalyst activity and stability. This wasunexpected as chromium (VI) is a strong oxidant and is known to promotethe crystallisation of chromia into an unstable and inactive crystallineform. Thus, the present invention is concerned particularly with achromium-containing fluorination catalyst which comprises an activityand stability promoting amount of chromium (VI) in an amount of from 0.1to 8.0% by weight based on the total weight of chromium in the catalyst.

The present invention also provides a process for the production offluorinated hydrocarbons which comprises reacting a hydrocarbon or ahalogenated hydrocarbon with hydrogen fluoride in the vapour phase inthe presence of a fluorination catalyst as herein defined.

In a preferred embodiment, the chromium-containing fluorinationcatalysts of the invention comprise one or more compounds selected fromthe chromium oxides, the chromium fluorides, fluorinated chromium oxidesand the chromium oxyfluorides.

The chromium compounds which make up the chromium-containing catalyst ofthe invention can contain chromium in any of its usual oxidation states,namely chromium (II), chromium (III) and chromium (VI). However, thebulk of the chromium compounds in the catalyst will usually be based onchromium (III) and, of course, from 0.1 to 8.0% by weight of thechromium based on the total weight of chromium in the catalyst must bepresent as chromium (VI).

DESCRIPTION OF THE DRAWING FIGURES

FIG. 1 is graph depicting the temperature required to achieve a 10%R-134a yield using catalysts having various chromium (VI) content (wt%).

FIG. 2 is a further graph depicting the temperature required to achievea 10% R-134a yield using catalysts having various chromium (VI) content(wt %).

DETAILED DESCRIPTION

Chromium (III) typically comprises from 92.0 to 99.9% by weight,preferably from 94.0 to 99.9% by weight, e.g. from 95.0 to 99.5% byweight, particularly from 96.0 to 99.5% by weight and especially from96.0 to 99.0% by weight, e.g. from 98.0 to 99.0% by weight of the totalweight of chromium in the catalyst. Chromium (VI) comprises from 0.1 to8.0% by weight, preferably from 0.1 to 6.0% by weight, e.g. from 0.5 to5.0% by weight, particularly from 0.5 to 4.0% by weight and especiallyfrom 1.0 to 4.0% by weight, e.g. from 1.0 to 2.0% by weight of the totalweight of chromium in the catalyst. As all the chromium is usuallypresent as chromium compounds, the percentages quoted above will alsonormally define the amounts of chromium (III) and chromium (VI)compounds in the catalyst based on the total weight of chromiumcompounds.

Chromium (III) compounds that may be present in the chromium-containingcatalyst of the invention include compounds selected from the groupconsisting of chromium (III) hydroxide, chromia (i.e. chromium (III)oxide), chromium (III) fluoride, fluorinated chromia and chromium (III)oxyfluorides. Chromium (VI) compounds that may be present in thecatalyst include compounds selected from the group consisting ofchromium (VI) oxide, chromic acid, fluorinated chromium (VI) oxide,chromium (VI) oxyfluorides and chromyl fluoride. The catalyst preferablycontains one or more chromium (III) compounds and one or more chromium(VI) compounds selected from the above groups of compounds. The preciseconstitution of the catalyst will depend, inter alia, on the methodsused for its preparation and whether the composition of the catalyst ismeasured pre- or post-fluorination.

Before the catalyst of the present invention is used in a fluorinationprocess or before it is subjected to a fluorination pre-treatment, asignificant proportion of the chromium, e.g. in excess of 50.0 weight %and more typically in excess of 75.0 weight % based on the total weightof chromium in the catalyst, is preferably present in the catalyst aschromium oxides, including chromia and chromium (VI) oxide. It may alsocontain an amount of chromium hydroxides, including chromium (III) andchromium (VI) hydroxides. The amounts of the chromium (III) oxides andhydroxides combined and the amounts of the chromium (VI) oxides andhydroxides combined are preferably as discussed above for the chromium(III) and chromium (VI) compounds generally. A preferredchromium-containing catalyst, pre-fluorination, has a molar ratio ofchromium (III) to oxygen to hydroxyl species (Cr (III):O:OH) in therange of from 1:0.5:2 to 1:1.5:0, preferably in the range of from 1:1:1to 1:1.5:0. This ratio can be readily determined using thermogravimetricanalysis. In one particular embodiment, the chromium-containingcatalyst, pre-fluorination, has a molar ratio of chromium (III) tooxygen to hydroxyl species (Cr (III):O:OH) in the range of from 1:0.5:2to 1:n:m, preferably in the range of from 1:1:1 to 1:n:m, where n isless than 1.5, m is greater than zero and 2n+m=3.0.

When the catalyst is used in a fluorination process, or when it issubjected to a fluorination pre-treatment to be described hereinafter, aproportion of the chromium oxides in the catalyst and any chromiumhydroxides that may be present will be converted to chromium fluorides,fluorinated chromium oxides and/or chromium oxyfluorides.

The zinc/chromia catalysts used in the present invention may beamorphous. By this we mean that the catalyst does not demonstratesubstantial crystalline characteristics when analysed, for example, byX-ray diffraction.

Alternatively, the catalysts may be partially crystalline. By this wemean that from 0.1 to 50% by weight of the catalyst is in the form ofone or more crystalline compounds of chromium and/or one or morecrystalline compounds of zinc. If a partially crystalline catalyst isused, it preferably contains from 0.2 to 25% by weight, more preferablyfrom 0.3 to 10% by weight, and particularly from 0.4 to 5% by weight ofone or more crystalline compounds of chromium and/or one or morecrystalline compounds of zinc.

In a preferred embodiment, the catalyst of the invention is an amorphousor partially crystalline catalyst comprising less than 8.0% by weight,e.g. less than 5.0% by weight, of crystalline compounds of chromiumand/or zinc based on the total weight of the catalyst. These catalystspreferably comprise greater than 3.0% by weight of zinc, e.g. fromgreater than 3.0 to 25.0% by weight, based on the total weight of thecatalyst.

The amount of crystalline material in the catalysts of the invention canbe determined by any suitable method known in the art. Suitable methodsinclude X-ray diffraction (XRD). When XRD is used, the amount ofcrystalline material, such as the amount of crystalline chromium oxide,can be determined with reference to a known amount of graphite presentin the catalyst (e.g. graphite used in producing catalyst pellets) or,more preferably, by comparison of the intensity of the XRD patterns ofthe sample materials with reference materials prepared by suitableinternationally recognised bodies, for example NIST (National Instituteof Standards and Technology), that contain a known amount of acrystalline material.

The zinc is usually present in the catalyst as a zinc compound and maybe present in or on the chromium-containing catalyst, that is the zincor compound of zinc may be incorporated in the chromium-containingcatalyst or it may be supported on the surface of the catalyst,depending at least to some extent upon the particular method employedfor preparing the catalyst. If the zinc is incorporated throughout thechromium-containing catalyst, as is preferred, then it is preferablysubstantially evenly distributed throughout the catalyst bulk.

In a preferred embodiment, the zinc is contained in aggregates whichhave a size across their largest dimension of up to 1 micron and whichare evenly distributed throughout at least the surface region of thecatalyst and wherein greater than 40 weight % of the aggregates containa concentration of zinc that is within ±1 weight % of the modalconcentration of zinc in those aggregates.

It has been found that the stability of chromium-containing catalystsincorporating controlled amounts of zinc can be improved if thedistribution of zinc in the catalyst meets the above criteria.

By the surface region of the catalyst, we are intending to refer to thatportion of the catalyst that will contact the hydrogen fluoride andorganic reactants during use. The surface of a catalyst is generallythat region where the coordination or valency of the atoms is notsatisfied when compared to the bulk material.

In this embodiment, the zinc-containing aggregates are preferably evenlydistributed throughout the entire catalyst bulk.

The aggregates have a size across their largest dimension of up to 1micron (1 μm), preferably in the range of from 20 nm to 1 μm, andgreater than 40 weight %, preferably greater than 50 weight %, morepreferably greater than 60 weight % and especially greater 70 weight %of the aggregates contain a concentration of zinc that is within ±1weight % of the modal concentration of zinc in those aggregates. In apreferred embodiment, greater than 80 weight %, more preferably greaterthan 85 weight %, and especially greater than 90 weight % of theaggregates contain a concentration of zinc that is within ±2 weight % ofthe modal concentration of zinc in those aggregates.

The modal concentration of zinc in the aggregates is that concentrationof zinc that occurs most frequently in the aggregates expressed as awhole number.

By ‘evenly distributed’ we include ‘substantially evenly distributed’and mean that the number or density of zinc-containing aggregates ineach region of the catalyst surface or the catalyst bulk, where the zincis dispersed throughout the entire catalyst, is substantially the same.For example, where the aggregates are only present at the catalystsurface, the number of aggregates in each square millimeter of thecatalyst surface is within ±2% of the mean number of aggregates persquare millimeter of the catalyst surface. Where the zinc-containingaggregates are distributed throughout the entire catalyst bulk, thenumber of aggregates in each square millimeter of the catalyst bulk iswithin ±2% of the mean number of aggregates per square millimeter of thecatalyst bulk.

The zinc is typically present in the catalyst in an amount of from 0.5to 25% by weight, e.g. from greater than 3 to 25% by weight, based onthe total weight of the catalyst. The amount of zinc is important,because at the right levels it will promote the activity of thechromium-containing catalyst. Too much zinc, on the other hand, mayresult in a decrease rather than an increase in catalyst activity.

The amount of zinc which will promote catalyst activity and produce acatalyst having an activity that is greater than the chromium-containingcatalyst alone depends, at least to some extent, on the surface area ofthe catalyst and whether the zinc is incorporated throughout thecatalyst bulk or just supported on its surface. Generally, the largerthe working surface area of the catalyst, the greater is the amount ofzinc which will be required to promote catalyst activity. Furthermore,catalysts containing zinc incorporated throughout their bulk, i.e. atsurface and non-surface locations, will tend to require larger amountsof zinc than those catalysts which only have zinc on their surface.

By way of example, in the case of a catalyst where the zinc isintroduced by impregnation to reside predominantly at the catalystsurface, activity promoting amounts of zinc for a chromium-containingcatalyst having a working surface area of between 20 and 50 m²/g areusually in the range of from about 0.5% to about 6.0% by weight based onthe total weight of the catalyst, preferably in the range of from about1.0% to about 5.0% by weight and especially in the range of from about2.0% to about 4.0% by weight.

However, for catalysts having larger working surface areas, for examplegreater than 100 m²/g, and comprising zinc distributed throughout thecatalyst bulk, the zinc may be present in an amount of from 5.0% toabout 25.0% by weight based on the total weight of the catalyst,preferably in an amount of from 5.0 to 20.0% by weight and especially inan amount of from 5.0 to 10.0% by weight.

For catalysts having small working surface areas, i.e. less than 20m²/g, for example about 5 m²/g, the amount of zinc may be as low as 0.5%to 1% by weight based on the total weight of the catalyst.

It should be understood that the amounts of zinc discussed above referto the amount of zinc itself, whether present as elemental zinc or as acompound of zinc. Thus, where the zinc is present as a compound of zinc,as is usual, the amounts refer to the zinc provided by the zinc compoundand not to the amount of the compound of zinc.

Preferred catalysts of the invention have a surface area in the range offrom 20.0 to 300.0 m²/g, more preferably in the range of from 100 to 250m²/g and particularly in the range of from 180 to 220 m²/g. Whenreferring to the surface area of the catalyst, we are referring to thesurface area prior to any fluorination treatment when measured by BETnitrogen isotherm (see, for example, G C Bond, HeterogeneousCatalysis—Principles and Applications 1987). These catalysts preferablycomprise from 0.5 to 25.0% by weight, e.g. from greater than 3.0% to25.0% by weight, more preferably from 0.5 to 10.0% by weight, e.g. fromgreater than 3.0% to 10.0% by weight, and particularly from 1.0 to 6.0%by weight, e.g. from greater than 3.0% to 6.0% by weight of zinc basedon the total weight of the catalyst. The zinc can be distributedthroughout the catalyst at surface and non-surface locations or just atthe surface.

Although the amount of zinc which will promote catalyst activity willvary depending, inter alia, on the surface area of the catalyst, uponthe distribution of zinc in the catalyst and upon the method that isused to prepare the catalyst, for any particular catalyst and catalystpreparation method, the amount of zinc that will promote catalystactivity is readily determined by routine experimentation using theabove percentages as a guide.

The chromium-containing catalyst may also comprise metal oxides,fluorinated metal oxides, metal fluorides or metal oxyfluorides otherthan chromium oxides, fluorinated chromium oxides, chromium fluorides orchromium oxyfluorides. The additional metal oxide may, for example, beselected from alumina, magnesia and zirconia, and in particular magnesiaand alumina, which during operation of the catalyst may be converted atleast in part to aluminium fluoride and magnesium fluoride respectively.

If desired, the catalyst may also contain one or more metals other thanzinc, for example nickel, cobalt or other divalent metals. Preferably,however, the chromium-containing catalyst will comprise just zinc,either as a metal but more typically as one or more zinc compounds.

The chromium-containing catalyst of the invention may also be supportedon a catalyst support material such as activated carbon or alumina.

The zinc promoter may be introduced into and/or onto thechromium-containing catalyst in the form of a compound, for example ahalide, oxyhalide, oxide or hydroxide, depending at least to some extentupon the catalyst preparation technique employed. When the zinc promoteris introduced by impregnating a chromium-containing catalyst, e.g. onecontaining one or more chromium (III) compounds and one or more chromium(VI) compounds, with a zinc compound, the zinc compound is preferably awater-soluble salt, for example a halide, nitrate or carbonate, and isimpregnated into the chromium-containing catalyst by contacting thecatalyst with an aqueous solution or slurry of the zinc compound.

In an alternative method for preparing the catalyst of the invention,the hydroxides of zinc and chromium are co-precipitated and thenconverted to their oxides by calcination to prepare a mixed oxidecatalyst.

If other metal oxides are to be included in the catalyst, such asalumina, then these can be introduced by co-precipitating the hydroxidesof chromium and the other metal and then converting the hydroxides totheir oxides by calcination to prepare a mixed oxide catalyst, e.g. ofchromium and aluminium oxides such as chromia and alumina. Zinc can beintroduced into the catalyst by impregnating the hydroxide or oxidemixture with an aqueous solution or dispersion of a zinc compound in themanner discussed above. Alternatively, zinc hydroxide can beco-precipitated with the hydroxides of chromium and the other metal andthe three hydroxides then converted simultaneously to their oxides bycalcination.

Mixing and milling of an insoluble zinc compound with the basic chromiumcontaining catalyst provides a further method of preparing the catalyst.

In a preferred embodiment, the catalysts of the present invention areprepared by adding zinc and chromium (III) salts to water and thenco-precipitating the hydroxides of zinc and chromium (III) by adding asuitable inorganic hydroxide and preferably ammonium hydroxide to theaqueous salt solution. The mixture of zinc and chromium hydroxides isthen collected, e.g. by filtration, washed, dried and calcined toconvert the hydroxides to their oxides. Any water soluble and stablesalts of zinc and chromium can be used including the chlorides,carbonates and nitrates. Preferred salts of chromium include chromiumnitrate and basic chromium nitrate (Cr(NO₃)₂.OH). A particularlysuitable chromium salt is chromium (III) nitrate. A preferred zinc saltis zinc nitrate.

The co-precipitation is preferably conducted under mixing conditionsthat will result in a catalyst in which the zinc or at least themajority of the zinc is contained in aggregates which have a size acrosstheir largest dimension of up to 1 micron and which are evenlydistributed throughout the entire catalyst bulk and wherein greater than40 weight % of the zinc-containing aggregates contain a concentration ofzinc that is within ±1 weight % of the modal concentration of zinc inthe zinc-containing aggregates.

The washing process following collection of the mixed hydroxideprecipitate can be important, because if the precipitate is preparedfrom a solution containing a nitrate salt then any nitrate that remainsfollowing the washing process can act as an oxidant to generate chromium(VI) from chromium (III) during the calcination process. More thoroughwashing of the collected precipitate, e.g. by repeated washing usingfresh batches of washing liquor, will tend to reduce the residualnitrate levels and hence the amount of nitrate that is available tooxidise the chromium (III) during the calcination step. Furthermore, thenature of the washing medium can influence the efficacy with whichnitrate contained in the mixed hydroxide precipitate is removed. Forexample, washing with an aqueous ammonia solution is more effective atremoving the nitrate than water alone. Thus, if the mixed hydroxideprecipitate is prepared from an aqueous solution containing chromium(III) and/or zinc nitrate, it is possible to control the level ofchromium (VI) in the catalyst following calcination by exercisingcontrol over the washing process, which in turn will affect the residuallevel of nitrate in the precipitate that is available to oxidise thechromium (III).

Where a calcination step is employed in the production of the catalystsof the invention, as is preferred, it typically involves heating theprecursor catalyst material at a temperature in the range of from 300 to450° C., more preferably in the range of from 300 to 400° C., forexample around 350° C. The calcination temperature that is used can alsoinfluence the level of chromium (VI) in the final catalyst. For example,if the catalyst is prepared by calcining a mixed hydroxide precipitateprepared from an aqueous solution containing chromium (III) and/or zincnitrate, then for a given level of residual nitrate following washing,higher calcination temperatures will tend to result in more of thechromium (III) being oxidised to chromium (VI). The calcination may beconducted in an inert atmosphere, e.g. of nitrogen, or it may beconducted in air or in an atmosphere comprising air or oxygen in mixturewith an inert gas such as nitrogen.

Another convenient way of generating the desired level of chromium (VI)compounds in the catalyst is by introducing a controlled amount of airinto the calcination step to oxidise the requisite proportion ofchromium (III) to chromium (VI). Here again, the calcination temperaturethat is used can also influence the level of chromium (VI) in the finalcatalyst, with higher calcination temperatures tending to encouragegreater oxidation of the chromium (III) for a given level of air.

The fluorination catalyst will usually be subjected to a fluorinationtreatment by heating in the presence of hydrogen fluoride, andoptionally an inert diluent, prior to being used in the catalysis offluorination reactions. A typical fluorination treatment comprisesheating the catalyst in the presence of hydrogen fluoride at atemperature in the range of from 250 to 450° C., more preferably in therange of from 300 to 380° C. and particularly in the range of from 350to 380° C. In a preferred embodiment, the fluorination treatment isconducted by contacting the fluorination catalyst with a mixture ofhydrogen fluoride and nitrogen. Conveniently, the treatment is conductedin the reactor in which the subsequent fluorination process is to beconducted by passing the hydrogen fluoride or hydrogen fluoride/nitrogenmixture through the reactor while it is heated.

Following the fluorination treatment, the working catalyst usuallycomprises at least a proportion of zinc fluoride in and/or on afluorinated chromium-containing catalyst material comprising one or morefluorine-containing chromium (III) compounds and one or morefluorine-containing chromium (VI) compounds selected from thefluorinated chromium oxides, the chromium fluorides and the chromiumoxyfluorides. Where the catalyst is a mixed oxide catalyst prepared byco-precipitation of chromium and zinc hydroxides followed by calcinationto convert the hydroxides to their oxides, as is preferred, thefluorination treatment usually converts at least a proportion of theoxides to oxyfluorides and fluorides.

The catalyst may be in the form of pellets or granules of appropriateshape and size for use in a fixed bed or a fluidised bed. Convenientlythe catalyst is in the form of cylindrically shaped pellets having alength and diameter in the range of from 1 to 6 mm, preferably in therange of from 2 to 4 mm, for example 3 mm.

After a period of use catalysing a fluorination reaction, the usedcatalyst may be regenerated or reactivated, for example by heating inair/nitrogen or air/hydrogen fluoride mixtures at a temperature of fromabout 300° C. to about 500° C. The regeneration or reactivation may beconducted periodically until the catalyst has reached the end of itsuseful lifetime. The catalyst may also be regenerated by passingchlorine through the reactor while heating the catalyst. Alternatively,the catalyst may be regenerated continuously while the process is beingoperated.

A further aspect of the present invention resides in the use of thezinc-promoted, chromium-containing catalyst in a fluorination process inwhich a hydrocarbon or halogenated hydrocarbon is reacted with hydrogenfluoride in the vapour-phase at elevated temperatures.

Accordingly, the present invention also provides a process for theproduction of fluorinated hydrocarbons which comprises reacting ahydrocarbon or a halogenated hydrocarbon with hydrogen fluoride atelevated temperature in the vapour phase in the presence of afluorination catalyst as herein defined.

Alkenes and alkanes as well as their halogenated counterparts containingat least one chlorine atom may be fluorinated using hydrogen fluorideand the catalysts of the present invention. Examples of specific vapourphase fluorinations which may be effected are the production of1,1,1,2-tetrafluoroethane from 1-chloro-2,2,2-trifluoroethane, theproduction of 1-chloro-2,2,2-trifluoroethane from trichloroethylene, theproduction of pentafluoroethane from dichlorotrifluoroethane, theproduction of dichlorotrifluoroethane, chlorotetrafluoroethane and/orpentafluoroethane from perchloroethylene and the conversion of1-chloro-2,2-difluoroethylene to 1-chloro-2,2,2-trifluoroethane.

The fluorination conditions employed when reacting the hydrocarbon orhalogenated hydrocarbon with hydrogen fluoride in the presence of thecatalyst of the invention may be those known in the art for fluorinationreactions that employ chromium-containing catalysts, for exampleatmospheric or super-atmospheric pressures and reactor temperatures inthe range of from 180° C. to about 500° C. When referring to the reactortemperature, we are referring to the mean temperature within thecatalyst bed. It will be appreciated that for an exothermic reaction,the inlet temperature will be lower than the mean temperature, and foran endothermic reaction, the inlet temperature will be greater than themean. The precise conditions will depend, of course, upon the particularfluorination reaction being carried out.

In a preferred embodiment, the catalyst of the invention is used in aprocess for preparing 1,1,1,2-tetrafluoroethane which comprises reacting1-chloro-2,2,2-trifluoroethane with hydrogen fluoride in the vapourphase at elevated temperatures in the presence of the catalyst. Reactiontemperatures in the range of from 250 to 500° C. are typically employed,with reaction temperatures in the range of from 280 to 400° C. beingpreferred and reaction temperatures in the range of from 300 to 350° C.being especially preferred. The process may be carried out underatmospheric or super-atmospheric pressures. Pressures of from 0 to 30barg are preferred whilst pressures of from 10 to 20 barg are especiallypreferred.

In a further preferred embodiment, the catalyst of the invention is usedin a multi-step process for preparing 1,1,1,2-tetrafluoroethane whichcomprises reacting trichloroethylene with hydrogen fluoride in thepresence of the catalyst to form 1-chloro-2,2,2-trifluoroethane. The1-chloro-2,2,2-trifluoroethane is then reacted with further hydrogenfluoride in the presence of the catalyst to form the1,1,1,2-tetrafluoroethane. The conversion of trichloroethylene to1-chloro-2,2,2-trifluoroethane and the conversion of1-chloro-2,2,2-trifluoroethane to 1,1,1,2-tetrafluoroethane may beconducted in discrete reaction zones of a single reactor, but they arepreferably conducted in different reactors. Both reactions are conductedat elevated temperatures in the vapour phase.

The preferred pressure and temperature conditions for the conversion of1-chloro-2,2,2-trifluoroethane to 1,1,1,2-tetrafluoroethane are asspecified above.

For the conversion of trichloroethylene to1-chloro-2,2,2-trifluoroethane, the process is typically conducted at atemperature in the range of from 180 to 300° C., preferably in the rangeof from 200 to 280° C. and particularly in the range of from 220 to 260°C. Atmospheric or super-atmospheric pressures may be employed in theprocess. Typically, the process is conducted at a pressure in the rangeof from 0 to 30 barg, preferably in the range of from 10 to 20 barg.

A particularly preferred embodiment of the above-described multi-stepprocess for preparing 1,1,1,2-tetrafluoroethane from trichloroethylenecomprises the steps of:

-   -   (A) in a first reaction zone reacting        1-chloro-2,2,2-trifluoroethane with hydrogen fluoride in the        vapour phase in the presence of a fluorination catalyst of the        invention at a temperature of from 250 to 450° C. so as to form        a product mixture containing 1,1,1,2-tetrafluoroethane and        hydrogen chloride together with unreacted starting materials;    -   (B) conveying the total product mixture of step (A) as well as        trichloroethylene and optionally further hydrogen fluoride to a        second reaction zone containing a fluorination catalyst of the        invention and in said second reaction zone reacting the        trichloroethylene with hydrogen fluoride in the vapour phase at        180 to 350° C. to form 1-chloro-2,2,2-trifluoroethane;    -   (C) collecting from step (B) a product mixture comprising        1-chloro-2,2,2-trifluoroethane, 1,1,1,2-tetrafluoroethane and        hydrogen chloride;    -   (D) treating the product of step (C) to recover        1,1,1,2-tetrafluoroethane and produce a composition comprising        1-chloro-2,2,2-trifluoroethane that is suitable for conveying to        the first reaction zone in step (A);    -   (E) conveying the 1-chloro-2,2,2-trifluoroethane composition        obtained from step (D) optionally together with further hydrogen        fluoride to said first reaction zone; and    -   (F) collecting 1,1,1,2-tetrafluoroethane recovered in step (D).

Although the process described above refers to first and second reactionzones, this should not be taken as limiting the process to a particularorder. In chemical terms, trichloroethylene is first converted to1-chloro-2,2,2-trifluoroethane and the 1-chloro-2,2,2-trifluoroethane isthen subsequently converted to 1,1,1,2-tetrafluoroethane. Thus, thefirst reaction in the reaction sequence is the hydrofluorination oftrichloroethylene to form 1-chloro-2,2,2-trifluoroethane. The first andsecond reaction zones may be provided by first and second reactors orthey may be discrete zones of a single reactor. Preferably, the firstand second reaction zones are provided by first and second reactors.

At least the stoichiometric amount of hydrogen fluoride is usuallyemployed in step (A) of the above process. Typically, from 1 to 10 molesof hydrogen fluoride and preferably from 1 to 6 moles of hydrogenfluoride are used per mole of 1-chloro-2,2,2-trifluoroethane.Accordingly, the product mixture of step (A) will usually containunreacted hydrogen fluoride in addition to 1,1,1,2-tetrafluoroethane,hydrogen chloride and by-products. It may also contain unreacted1-chloro-2,2,2-trifluoroethane. Preferred reaction temperatures for step(A) are in the range of from 250 to 500° C., more preferably in therange of from 280 to 400° C. and particularly in the range of from 300to 350° C. Preferred reaction pressures for step (A) are in the range offrom 0 to 30 barg, more preferably in the range of from 10 to 20 barg,for example around 15 barg. Preferred residence times in the firstreaction zone are in the range of from 1 to 600 seconds, more preferablyin the range of from 1 to 300 seconds and particularly in the range offrom 1 to 100 seconds.

In step (B), usually from 10 to 50 moles of hydrogen fluoride andpreferably from 12 to 30 moles of hydrogen fluoride per mole oftrichloroethylene are employed. Again, the reaction product of thisstage will normally contain unreacted hydrogen fluoride and may alsocontain unreacted trichloroethylene. Preferred reaction temperatures forstep (B) are in the range of from 180 to 300° C., more preferably in therange of from 200 to 300° C. and particularly in the range of from 220to 280° C. Preferred reaction pressures for step (B) are in the range offrom 0 to 30 barg, more preferably in the range of from 10 to 20 barg,for example around 15 barg. Preferred residence times in the firstreaction zone are in the range of from 1 to 600 seconds, more preferablyin the range of from 1 to 300 seconds and particularly in the range offrom 1 to 100 seconds.

Although the reactant mixtures that are conveyed to the first and secondreaction zones must include hydrogen fluoride, this does not mean that afresh or virgin supply of material has to be delivered to both reactionzones. For example, the process can be operated so that virgin hydrogenfluoride is only introduced into the second reaction zone in sufficientexcess that enough unreacted hydrogen fluoride can be recovered from theproduct mixture exiting step (B) to drive the hydrofluorination reactionthat occurs in the first reaction zone in step (A). One possibility isto operate step (D) of the process so that the1-chloro-2,2,2-trifluoroethane composition that is collected alsocontains hydrogen fluoride in a sufficient quantity for the reaction inthe first reaction zone. Alternatively, the process can be operated sothat virgin hydrogen fluoride is only introduced into the first reactionzone in sufficient excess that enough hydrogen fluoride remains in theproduct mixture of step (A) that is conveyed to the second reaction zonefor reaction with the trichloroethylene. Additionally, after start up,the hydrogen fluoride required for the hydrofluorination reactions inthe first and second reaction zones could even be introduced into adistillation column used to conduct step (D) of the process.

The reaction and separation steps which make up the preferred multi-stepprocess for making 1,1,1,2-tetrafluoroethane may be performed usingconventional equipment and techniques. Step (D), which is effectively aseparation/purification step in which the useable components making upthe product collected from step (B) are substantially separated from oneanother, may be effected by conventional distillation, phase separationand washing/scrubbing processes known to those skilled in the art.

The operation of the preferred multi-step process for making1,1,1,2-tetrafluoroethane is described more particularly inEP-A-0449617.

In another preferred embodiment, the catalyst of the invention is usedin a process for preparing pentafluoroethane which comprises reactingdichlorotrifluoroethane with hydrogen fluoride in the vapour phase atelevated temperatures in the presence of the catalyst. Reactiontemperatures of at least 280° C., e.g. in the range of from 280 to 400°C., are typically employed, with reaction temperatures in the range offrom 280 to 380° C. being preferred and reaction temperatures in therange of from 300 to 360° C. being especially preferred. The process maybe carried out under atmospheric or super-atmospheric pressures.Typically, the process is conducted at a pressure of from 0 to 30 barg,preferably at a pressure of from 12 to 22 barg and more preferably at apressure of from 14 to 20 barg.

In yet another preferred embodiment, the catalyst of the invention isused in a multi-step process for preparing pentafluoroethane whichcomprises reacting perchloroethylene with hydrogen fluoride in thepresence of the catalyst to form dichlorotrifluoroethane. Thedichlorotrifluoroethane is then reacted with further hydrogen fluoridein the presence of the catalyst to form the pentafluoroethane. Theconversion of perchloroethylene to dichlorotrifluoroethane and theconversion of dichlorotrifluoroethane to pentafluoroethane may beconducted in discrete reaction zones of a single reactor, but they arepreferably conducted in different reactors. Both reactions are conductedat elevated temperatures in the vapour phase.

The preferred pressure and temperature conditions for the conversion ofdichlorotrifluoroethane to pentafluoroethane are as specified above.

For the conversion of perchloroethylene to dichlorotrifluoroethane, theprocess is typically conducted at a temperature in the range of from 200to 350° C., preferably in the range of from 230 to 330° C. andparticularly in the range of from 240 to 310° C. Atmospheric orsuper-atmospheric pressures may be employed in the process. Typically,the process is conducted at a pressure in the range of from 0 to 30barg, preferably at a pressure in the range of from 10 to 20 barg andmore preferably at a pressure in the range of from 12 to 18 barg.

A particularly preferred embodiment of the above-described multi-stepprocess for preparing pentafluoroethane from perchloroethylene comprisesthe steps of:

-   -   (A), in a first reactor or a first plurality of reactors        reacting perchloroethylene with hydrogen fluoride in the vapour        phase at a temperature of from 200 to 350° C. in the presence of        a chromium-containing fluorination catalyst of the invention to        produce a composition comprising dichlorotrifluoroethane,        hydrogen chloride, unreacted hydrogen fluoride and        perchioroethylene, less than 2 weight % of        chlorotetrafluoroethane and pentafluoroethane combined and less        than 5 weight % of compounds having the formula C₂Cl_(6-x)F_(x),        where x is an integer of from 0 to 6, based on the total weight        of organic compounds in the composition;    -   (B) subjecting the composition from step (A) to a separation        step to yield a purified composition comprising at least 95        weight % of dichlorotrifluoroethane and less than 0.5 weight %        of compounds having the formula C₂Cl_(6-x)F_(x), where x is an        integer of from 0 to 6, based on the total weight of organic        compounds in the composition; and    -   (C) in a second reactor or a second plurality of reactors        reacting the composition from step (B) with hydrogen fluoride in        the vapour phase at a temperature of at least 280° C. in the        presence of a chromium-containing fluorination catalyst of the        invention to produce a composition comprising pentafluoroethane        and less than 0.5 weight % of chloropentafluoroethane, based on        the total weight of organic compounds in the composition.

By compounds of formula C₂Cl_(6-x)F_(x), where x is from 0 to 6, weinclude trichlorotrifluoroethane and dichlorotetrafluoroethane.

In step (A), from 3 to 50 moles of hydrogen fluoride are usuallyemployed per mole of perchloroethylene. Preferably, from 4 to 20 molesof hydrogen fluoride and more preferably from 4 to 10 moles of hydrogenfluoride are used per mole of perchioroethylene. Preferred reactiontemperatures and pressures for step (A) are as discussed above for theconversion of perchioroethylene to dichlorotrifluoroethane. Preferredresidence times for the reactants in the first reactor in step (A) arein the range of from 10 to 200 seconds, more preferably in the range offrom 30 to 150 seconds and particularly in the range of from 60 to 100seconds.

In step (C), from 2 to 20 moles of hydrogen fluoride are usuallyemployed per mole of dichlorotrifluoroethane. Preferably, from 2 to 10moles of hydrogen fluoride and more preferably from 2 to 6 moles ofhydrogen fluoride are used per mole of dichlorotrifluoroethane.Preferred reaction temperatures and pressures for step (C) are asdiscussed above for the conversion of dichlorotrifluoroethane topentafluoroethane. Preferred residence times for the reactants in thesecond reactor in step (C) are in the range of from 10 to 200 seconds,more preferably in the range of from 20 to 100 seconds and particularlyin the range of from 30 to 60 seconds.

The reaction and separation steps which make up the preferred multi-stepprocess for making pentafluoroethane may be performed using conventionalequipment and techniques. Separation step (B) may, for example, beeffected using conventional distillation, phase separation andwashing/scrubbing processes known to those skilled in the art.

The operation of the preferred multi-step process for makingpentafluoroethane is described more particularly in WO 2007/068962.

It is preferred to operate processes that use the catalyst of theinvention continuously, except for any shut-down time that is necessaryto regenerate or reactivate a catalyst that has been deactivated thoughuse. The feeding of air to the catalyst during operation of the processmay counter catalyst deactivation and reduce the frequency of processshut-downs for catalyst regeneration.

The present invention is now illustrated but not limited by thefollowing examples.

General Procedures:

Catalyst Preparation:

A mixture of zinc and chromium (III) hydroxides was made byco-precipitation from an aqueous solution of zinc and chromium (III)nitrates using ammonium hydroxide (12.5% w/w ammonia in deionisedwater). The solution of zinc and chromium nitrates contained a chromiumcontent of approximately 10% w/w and a zinc content of approximately1.3% w/w to achieve a loading of zinc in the finished catalystformulation of around 8.0 weight %. The equipment employed comprised acooled and stirred 300 ml precipitation tank which was fed with anaqueous stream comprising the zinc and chromium nitrates and a separatestream of ammonium hydroxide. The tank stirrer was rotated at 500 rpmduring catalyst preparation. The mixed-nitrates feed and ammoniumhydroxide feed were injected continuously into the tank at a point closeto the stirrer blade to ensure rapid mixing. The mixed-hydroxide productformed in the precipitation tank was collected at an overflow pointwhich maintained a constant slurry volume of approximately 200 ml in theprecipitation tank during a catalyst preparation. The vessel walls werecooled to maintain a temperature of 14 to 15° C. and the ammoniumhydroxide pumping rate adjusted to maintain the pH of the slurry in therange of 7 to 8.5.

400 ml batches of slurry from the precipitation tank were filtered torecover the co-precipitated hydroxides, which were then washed andfiltered further. The degree of washing was important, since itdetermined the residual level of oxidants and particularly nitrate saltsthat were available to generate the Cr(VI) during calcination. Eitherwater or water doped with varying amounts of a 25% aqueous ammoniasolution were used as the washing medium and either single or multiplewashes were conducted.

The batches of washed solid were then dried at 100° C. overnight in anitrogen atmosphere, powdered to pass through a 0.5 mm sieve and mixedwith 2% w/w graphite. 2 to 3 g batches of this lubricated powder werethen pressed into 13 mm diameter discs using an applied pressure of 5tonnes. The compacted hydroxide discs were then crushed and sieved togenerate particles in the size range 0.5 to 1.4 mm for calcination andsubsequent catalyst testing.

6 g batches of the compacted and crushed hydroxide materials werecharged to a 12.7 mm (½″) diameter calcination tube purged with 60ml/min of nitrogen. The catalyst batches were then calcined by heatingto either 300° C. or 350° C. for a period of four hours and finallycooled under nitrogen to room temperature to generate the finishedcatalysts for performance testing. It is during the calcination stagethat the Cr(VI) is generated.

Measurement of Chromium (VI) Content:

The chromium (VI) level in the catalyst samples was measured byreduction. A small sample of catalyst was loaded into an Inconel U-tubereactor and the reactor purged with a mixture of hydrogen (15 ml/min)and nitrogen (60 ml/min) at room temperature. The reduction was theninitiated by placing the U-tube containing the catalyst into an ovenpre-heated to 370° C. The gas stream exiting the reactor was fed to agas chromatogram equipped with a thermal conductivity detector (TCD) todetermine the amount of hydrogen consumed during the reduction fromwhich the level of chromium (VI) in the catalyst could be calculated.

The chromium (VI) level could also be determined by reduction in athermogravimetric analyser, using the weight loss to determine thechromium (VI) level.

Catalyst Testing:

The performance of the catalysts was investigated using a catalyst testrig that contained 4 reactor tubes each with independent HF andtrichloroethylene feeds. Each reactor was charged with 2 g of catalystin the particle size range 0.5 to 1.4 mm. Nitrogen at a flow rate of 60ml/min was then directed to the reactor inlets and the catalyst samplesdried in the nitrogen stream at 250° C. for 1 hour.

After drying, HF was fed to each reactor by means of a sparge system. A5 ml/min flow of nitrogen was passed through liquid HF at a constant 8°C. to give a 30 ml/min flow of HF gas which was then passed to eachreactor along with a 60 ml/min flow of nitrogen. The reactors wereheated to 250° C. and the HF/nitrogen mixture passed over the catalystsamples for approximately 30 minutes until HF was observed in thereactor off gas. At this point, the 60 ml/min nitrogen flow wasredirected to the reactor exit. The catalyst samples were then exposedto the HF:N₂ (30:5 ml/min) stream for a further one hour at 250° C.before ramping the temperature to 460° C. at 40° C. per hour thenholding at 460° C. overnight.

The following day the reactors were cooled to 350° C. andtrichloroethylene was fed to the catalyst in each reactor by sparging a5 ml/min flow of nitrogen through liquid trichloroethylene (TRI) at roomtemperature to give a 1 ml/min flow of trichloroethylene gas. Thecatalyst was allowed to equilibrate in the HF:TRI:N₂ (30:1:10 ml/min)gas stream for about 2 hours before reducing the temperature to 300° C.The catalyst was allowed to equilibrate at 300° C. for about 1 hourbefore measuring the production of 1-chloro-2,2,2-trifluoroethane(R-133a) and 1,1,1,2-tetrafluoroethane (R-134a) by gas chromatography(GC). Using the R-134a yield, the temperature required to give a 10%134a yield was then calculated.

The trichloroethylene feed was then switched off and the catalystsamples were thermochemically “aged” by heating them at 500° C. in theHF stream overnight. The reactors were then cooled to 350° C. andoperated as before to prepare R-134a from trichloroethylene. Thecatalyst activity was investigated by determining the temperaturerequired to give a 10% yield of R-134a from trichloroethylene. Thisactivity was taken to be the initial activity of the catalyst, becausecatalysts tend to take some time to bed in before they operate atoptimum levels.

The trichloroethylene feed was then switched off once again and thecatalyst samples were thermochemically “aged” still further by heatingthem at 519° C. in the HF stream overnight. This additional ageing wasconducted to investigate the stability of the catalysts. After theadditional ageing, the reactors were cooled to 350° C. and operated asbefore to prepare R-134a from trichloroethylene. The stability of thecatalysts was assessed by determining the temperature required to give a10% yield of R-134a from trichloroethylene. After thermal ageing at 519°C., the more stable catalysts were those that gave a 10% conversion oftrichloroethylene to R-134a at lower temperatures.

EXAMPLE 1

A series of zinc promoted chromia catalysts were prepared using theabove described general procedure. The washing of the filtered mixedhydroxide precipitates was varied from catalyst to catalyst, with boththe washing medium and the number of washing cycles being varied. Allthe catalysts were calcined at 300° C. for 4 hours under nitrogen. Theamount of chromium (VI) in the mixed oxide catalysts that were obtainedfollowing calcination was assessed using the general procedure describedabove.

The washing processes that were used and the amount of chromium (VI) inthe resulting catalysts are reported in Table 1 below.

It is evident from the results reported in Table 1, that water dosedwith 25% aqueous ammonia is a more effective washing medium than wateralone, removing more of the oxidising nitrate salts and giving rise tomixed oxide catalysts that under the same calcination conditions havesmaller amounts of chromium (VI). It is also evident that multiplewashing cycles will tend to remove more of the oxidising nitrate salts,once again resulting in catalysts that under the same calcinationconditions have smaller amounts of chromium (VI).

It was found that the Cr(VI) levels in the final mixed oxide catalystcould be manipulated in the range 0 to 12 wt % by adjusting the washingprocedure and washing medium.

EXAMPLE 2

Two zinc promoted chromia catalysts were prepared using the abovedescribed general procedure. The washing of the filtered mixed hydroxideprecipitates was the same in each case. One precipitate was calcined at300° C. for 4 hours and the other at 350° C. for 4 hours. The amount ofchromium (VI) in the mixed oxide catalysts that were obtained followingcalcination was then assessed using the general procedure describedabove. The results are reported in Table 2 below.

It is apparent from the results recorded in Table 2, that calcining at350° C. instead of 300° C. caused a dramatic increase in the level ofchromium (VI).

EXAMPLE 3

A series of zinc promoted chromia catalysts were prepared using theabove described general procedure. The washing of the filtered mixedhydroxide precipitates was varied from catalyst to catalyst in order toobtain mixed oxide catalysts with varying amounts of chromium (VI). Allthe catalysts were calcined at 300° C. The amount of chromium (VI) inthe mixed oxide catalysts that were obtained following calcination wasassessed using the general procedure described above.

Each catalyst was then tested in accordance with the general proceduredescribed above to prepare R-134a from trichloroethylene.

The initial activity of the catalysts after ageing at 500° C. isrecorded in FIG. 1. It is evident, that as the level of chromium (VI) inthe catalyst is increased up to 8.0 weight %, that the temperaturerequired to achieve a 10% R-134a yield reduces. Low operatingtemperatures indicate a more active catalyst, with reduced by-productformation and less fouling. Beyond around 4.0 weight %, the impact offurther chromium (VI) is much less significant.

The stability of the catalysts after ageing at 519° C. is recorded inFIG. 2. It is evident, that as the level of chromium (VI) in thecatalyst is increased up to 8.0 weight % that lower temperatures wererequired to achieve a 10% R-134a yield. The effect beyond 4.0 weight %was much less significant. Thus, catalysts containing chromium (VI)exhibit greater stability. More stable catalysts means longer catalystlife and reduced costs.

TABLE 1 Amount of 25% pH during Number of NH₃ added to precipitationwashes wash water (g/l) Cr(VI) wt % 7-7.5 1 0 12.4 7-7.5 2 0 8.0 7-7.5 30 7.1 7-7.5 4 0 6.3 7-7.5 1 1 12.4 7-7.5 2 1 6.3 7-7.5 3 1 5.0 7-7.5 4 14.0 7-7.5 1 4 12.0 7-7.5 2 4 4.1 7-7.5 3 4 3.0 7-7.5 4 4 0.6 7-7.5 1 811.2 7-7.5 2 8 2.2 7-7.5 3 8 1.6 7-7.5 4 8 0.8

TABLE 2 Amount of 25% Calcination pH during Number of NH₃ added toTemperature precipitation washes wash water (g/l) (° C.) Cr(VI) wt %7-7.5 4 4 300 0.6 7-7.5 4 4 350 3.3

The invention claimed is:
 1. A chromium-containing fluorination catalystcomprising from greater than 3 to 25% by weight of zinc based on thetotal weight of the catalyst, wherein from 0.5% to 4.0% by weight of thechromium in the catalyst based on the total weight of said chromium ispresent as chromium (VI) with the balance of the chromium present in thecatalyst as chromium (III) and wherein the catalyst is amorphous orpartially crystalline comprising less than 5.0% by weight of crystallinecompounds of chromium and/or zinc.
 2. The catalyst of claim 1, whereinfrom 1.0 to 4.0% by weight of the chromium in the catalyst based on thetotal weight of said chromium is present as chromium (VI).
 3. Thecatalyst of claim 2, wherein from 96.0 to 99.0% by weight of thechromium in the catalyst based on the total weight of said chromium ispresent as chromium (III).
 4. The catalyst claim 1, wherein the catalystcomprises one or more chromium (VI) compounds selected from the groupconsisting of chromium (VI) oxide, chromic acid, fluorinated chromium(VI) oxide, chromium (VI) oxyfluorides and chromyl fluoride.
 5. Thecatalyst claim 1, wherein the catalyst comprises one or more chromium(III) compounds selected from the group consisting of chromia, chromium(III) fluoride, fluorinated chromia and chromium (III) oxyfluorides. 6.The catalyst of claim 5, wherein the catalyst has been subjected to acalcination process and then subsequently fluorinated.
 7. The catalystclaim 1, wherein the zinc is present in the catalyst in an amount offrom greater than 3 to 10% by weight based on the total weight of thecatalyst.
 8. The catalyst of claim 7, wherein the zinc is present in thecatalyst in an amount of from greater than 3 to 8% by weight based onthe total weight of the catalyst.
 9. The catalyst claim 1, wherein thesurface area of the catalyst is in the range of from 20 to 300 m²/g. 10.The catalyst of claim 9, wherein the surface area of the catalyst is inthe range of from 100 to 250 m²/g.
 11. A process for the production offluorinated hydrocarbons which comprises reacting a hydrocarbon or ahalogenated hydrocarbon with hydrogen fluoride at elevated temperaturein the vapour phase in the presence of a fluorination catalyst asclaimed in claim
 1. 12. The process of claim 11, wherein1-chloro-2,2,2-trifluoroethane is reacted with hydrogen fluoride in thepresence of the catalyst to produce 1,1,1,2-tetrafluoroethane.
 13. Theprocess of claim 11, wherein trichloroethylene is reacted with hydrogenfluoride in the presence of the catalyst to produce1-chloro-2,2,2-trifluoroethane.
 14. The process of claim 11, whereindichlorotrifluoroethane is reacted with hydrogen fluoride in thepresence of the catalyst to produce pentafluoroethane.
 15. The processof claim 11, wherein perchloroethylene is reacted with hydrogen fluoridein the presence of the catalyst to produce dichlorotrifluoroethane,chlorotetrafluoroethane and/or pentafluoroethane.